/*
 * Copyright 1999-2017 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package studio.raptor.sqlparser.visitor.functions;

import static studio.raptor.sqlparser.visitor.SQLEvalVisitor.EVAL_VALUE;

import java.util.List;
import studio.raptor.sqlparser.ast.SQLExpr;
import studio.raptor.sqlparser.ast.expr.SQLMethodInvokeExpr;
import studio.raptor.sqlparser.visitor.SQLEvalVisitor;

public class Lpad implements Function {

  public final static Lpad instance = new Lpad();

  public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
    List<SQLExpr> params = x.getParameters();
    int paramSize = params.size();
    if (paramSize != 3) {
      return SQLEvalVisitor.EVAL_ERROR;
    }

    SQLExpr param0 = params.get(0);
    SQLExpr param1 = params.get(1);
    SQLExpr param2 = params.get(2);

    param0.accept(visitor);
    param1.accept(visitor);
    param2.accept(visitor);

    Object param0Value = param0.getAttributes().get(EVAL_VALUE);
    Object param1Value = param1.getAttributes().get(EVAL_VALUE);
    Object param2Value = param2.getAttributes().get(EVAL_VALUE);
    if (param0Value == null || param1Value == null || param2Value == null) {
      return SQLEvalVisitor.EVAL_ERROR;
    }

    String strValue0 = param0Value.toString();
    int len = ((Number) param1Value).intValue();
    String strValue1 = param2Value.toString();

    String result = strValue0;
    if (result.length() > len) {
      return result.substring(0, len);
    }

    while (result.length() < len) {
      result = strValue1 + result;
    }

    return result;
  }
}
